CN102447659B

CN102447659B - A kind of signal processing method based on single carrier frequency domain equalization, Apparatus and system

Info

Publication number: CN102447659B
Application number: CN201210004605.9A
Authority: CN
Inventors: 高健; 易鸿
Original assignee: ZTE Corp
Current assignee: ZTE Corp
Priority date: 2012-01-09
Filing date: 2012-01-09
Publication date: 2015-09-16
Anticipated expiration: 2032-01-09
Also published as: WO2013104184A1; CN102447659A

Abstract

The invention discloses a kind of signal processing method based on single carrier frequency domain equalization (SC-FDE), comprise: light sender produces unique word (UW) sequence and synchronizing data blocks, with UW sequence composition Frame, by synchronizing data blocks and Frame composition super frame, super frame is sent to light receiver as baseband signal.The present invention also also discloses a kind of signal processing system based on SC-FDE, adopts the present invention can simplify light sender hardware device and reduces the cost of light sender, and improving the accuracy of time synchronized, and the process resource taken when reducing channel estimating.

Description

Signal processing method, device and system based on single carrier frequency domain equalization

Technical Field

The invention relates to a signal processing technology in the field of optical fiber communication, in particular to a signal processing method, a signal processing device and a signal processing system based on Single Carrier-Frequency Domain Equalization (SC-FDE).

Background

In the signal transmission process of the optical fiber communication system, due to the conditions of Dispersion and Polarization Mode Dispersion (PMD) caused by high-rate transmission, distortion and distortion of a transmission channel are caused, and the distortion of the transmission channel further cause intersymbol interference, which is a main factor affecting the communication quality in the optical fiber communication system. Therefore, SC-FDE technology is used in fiber optic communication systems to solve the intersymbol interference problem.

One method for solving the problem of intersymbol interference in the SC-FDE technology is a signal processing method for inserting a training sequence, and specifically includes: forming a Data frame by using the training sequence as a Unique Word (UW) and Data (Data) to be transmitted in an optical transceiver, and transmitting a modulated signal after the Data frame is modulated to the optical receiver; the optical receiver demodulates the received modulation signal to obtain a demodulated data frame, and then performs time synchronization, frequency offset estimation and channel estimation by using the UW in the demodulated data frame.

The structure of the data frame is shown in fig. 1, and the data frame is composed of two UWs and data, wherein one UW is overlapped between each frame of data; the UW is a sequence with the length of M +2L, and the method for forming the UW comprises the following steps: firstly, generating a specific sequence with the length of M, copying last L symbols in the specific sequence, adding the copied last L symbols to the sequence with the length of M to form a prefix, copying first L symbols in the specific sequence, adding the copied first L symbols to the sequence with the length of M to form a suffix, and forming UW with the length of M + 2L. The specific sequence with the length M uses a constant envelope Zero Auto-correlation (CAZAC) sequence as an optimal sequence. The performing time synchronization, frequency offset estimation and channel estimation by using the UW in the demodulated data frame includes: the method for time synchronization in the prior art is a Schmidl method, frequency offset estimation is obtained based on time synchronization calculation, and channel estimation adopts a maximum likelihood estimation method.

However, the above method of inserting the training sequence has the following problems:

firstly, a high-end Digital-to-Analog Converter (DAC) is required to transmit a data frame composed of a CAZAC sequence, and the high-end DAC is complex in structure and high in price;

secondly, in the Schmidl synchronization calculation method used for time synchronization by the signal processing method, the problem that the determined synchronization position is not accurate enough can occur due to the fact that the front UW and the rear UW in the demodulated data frame are the same, and the problem that a correlation peak is not sharp enough exists in the Schmidl synchronization calculation method;

third, the maximum likelihood estimation method used in the channel estimation of the signal processing method requires a large number of matrix and inverse matrix operations, which results in a large amount of operations and thus occupies a large processing resource of the optical receiver.

It can be seen that the existing signal processing method for inserting training sequence cannot simplify the hardware equipment of the optical transmitter and reduce the cost of the optical transmitter, and cannot ensure the accuracy of time synchronization, and occupies a large processing resource of the optical receiver during channel estimation.

Disclosure of Invention

In view of the above, an objective of the present invention is to provide a signal processing method, device and system based on SC-FDE, which simplify hardware devices of an optical transmitter, reduce cost of the optical transmitter, improve accuracy of time synchronization, and reduce processing resources occupied during channel estimation.

In order to achieve the purpose, the technical scheme of the invention is realized as follows:

the invention provides a signal processing method based on SC-FDE, which comprises the following steps:

the optical transmitter generates a UW sequence and a synchronous data block, the UW sequence is used for forming a data frame, the synchronous data block and the data frame are used for forming a super frame, and the super frame is used as a baseband signal to be sent to the optical receiver.

In the above scheme, the generating a UW sequence includes: the UW sequence was composed using binary sequences selected according to the following conditions:

wherein u (n) is a UW sequence, M is the length of the UW sequence, and k is 0, 1.

u(n)∈{+1，-1}，n＝0，1，...，M-1；

The length of the u (n) sequence is a multiple of 4;

the M/2-1 and M-1 in u (n) are set to-1;

the first half and the second half of the UW sequence are in a complementary relationship:

u(n)＝-u(n+M/2)，n＝0，...，M/2-2。

in the above scheme, the synchronization data block is: the method comprises A, B, C three sections of synchronization sequences, wherein the A section of synchronization sequence is L bits long, and the B and C synchronization sequences are both N bits long; wherein, the L bits of data of the a sync sequence are a binary sequence s' (N) (N ═ N/2-L.., N/2-1); the B and C synchronization sequences are sync (N), sync (N) s' (N) x (N), and x (N) is a binary sequence of length N, and the conditions for selecting x (N) binary sequences are the same as those for selecting binary sequences when generating UW sequences;

whereinSaid s' (n) may be dependent on conditions

And (6) selecting.

In the foregoing solution, after sending the superframe as a baseband signal to the optical receiver, the method further includes: after receiving the baseband signal from the optical transmitter, the optical receiver performs sliding calculation on the received super frame by using the synchronous data block to perform time synchronization, and performs correlation calculation by using the UW sequence to obtain a channel estimation value.

In the above scheme, the performing sliding computation on the received superframe by using the synchronous data block to perform time synchronization includes:

the optical receiver respectively reads data of which the length is greater than the sum of the lengths of the B and C synchronous sequences in the synchronous data block in the baseband signals of the two polarization states;

performing sliding calculation on the read partial baseband signal data by using a sequence which is generated by the optical transceiver and has the length of a B or C synchronization sequence in the synchronization data block and is the same as a binary sequence used when the optical transceiver generates the synchronization data block;

and the demodulated baseband signal data corresponding to the maximum value in the sliding calculation result is the time synchronization position.

In the foregoing solution, before the obtaining the channel estimation value by using the UW sequence to perform the correlation calculation, the method further includes: the optical receiver carries out frequency deviation estimation on the baseband signals after time synchronization; and eliminating the carrier frequency deviation according to the result of the frequency deviation estimation, and performing channel estimation on the baseband signal after the carrier frequency deviation is eliminated.

In the foregoing solution, the performing channel estimation on the baseband signal without carrier frequency offset includes: the optical receiver generates a UW sequence with the length of M according to the mode that the optical receiver generates the UW sequence, and performs correlation calculation by using the UW sequence generated by the optical receiver and the baseband signal with the carrier frequency deviation eliminated, so as to obtain a channel estimation result.

after receiving the baseband signal from the optical transmitter, the optical receiver performs sliding calculation on the received super frame by using the synchronous data block to perform time synchronization, and performs correlation calculation by using the UW sequence to obtain a channel estimation value.

In the above solution, before the optical receiver receives the baseband signal sent by the optical transmitter, the method further includes: the optical transmitter generates a UW sequence and a synchronous data block, the UW sequence is used for forming a data frame, the synchronous data block and the data frame are used for forming a super frame, and the super frame is used as a baseband signal to be sent to the optical receiver.

u(n)∈{+1，-1}，n＝0，1，...，M-1；

The length of the u (n) sequence is a multiple of 4;

the M/2-1 and M-1 in u (n) are set to-1;

u(n)＝-u(n+M/2)，n＝0，...，M/2-2。

wherein s' (n) may be according to conditions

And (6) selecting.

The invention also provides a signal processing system based on SC-FDE, which comprises: an optical transmitter and an optical receiver; wherein,

the optical transmitter is used for generating a UW sequence and a synchronous data block, forming a data frame by using the UW sequence, forming a super frame by using the synchronous data block and the data frame, and transmitting the super frame to the optical receiver as a baseband signal;

and the optical receiver is used for performing sliding calculation on the received super frame by using the synchronous data block to perform time synchronization after receiving the baseband signal transmitted by the optical transmitter, and then performing channel estimation by using the UW sequence.

The present invention provides an optical transponder comprising: the device comprises a sending signal processing module and an optical modulation module; wherein,

the transmission signal processing module is used for generating a UW sequence and a synchronous data block, forming a data frame by using the UW sequence, forming a super frame by using the synchronous data block and the data frame, and transmitting the super frame to the light modulation module;

and the optical modulation module is used for receiving the superframe sent by the sending signal processing module as a baseband signal, modulating the baseband signal and then sending the modulated baseband signal to the optical receiver.

In the foregoing scheme, the transmit signal processing module is specifically configured to use a binary sequence to form a UW sequence, and select the binary sequence according to the following conditions:

u(n)∈{+1，-1}，n＝0，1，...，M-1；

The length of the u (n) sequence is a multiple of 4;

the M/2-1 and M-1 in u (n) are set to-1;

u(n)＝-u(n+M/2)，n＝0，...，M/2-2。

in the above scheme, the transmission signal processing module is specifically configured to be composed of A, B, C three segments of synchronization sequences, where a segment a is L bits long, and B and C are both N bits long; wherein, the L bits of data of the a sync sequence are a binary sequence s' (N) (N ═ N/2-L.., N/2-1); the B and C synchronization sequences are sync (N), sync (N) s' (N) x (N), and x (N) is a binary sequence of length N, and the conditions for selecting x (N) binary sequences are the same as those for selecting binary sequences when generating UW sequences;

wherein s' (n) may be according to conditions

And (6) selecting.

The present invention also provides an optical receiver including: a received signal processing module and an optical demodulation module; wherein,

the optical demodulation module is used for receiving the modulation signal sent by the optical transmitter, demodulating the modulation signal to obtain a baseband signal and sending the demodulated baseband signal to the received signal processing module;

and the received signal processing module is used for performing sliding calculation on the received super frame by using the synchronous data block to perform time synchronization after receiving the baseband signal sent by the optical demodulation module, and then performing channel estimation by using the UW sequence.

In the above scheme, the received signal processing module is specifically configured to read data in two polarization baseband signals, where the length of the data is greater than the sum of lengths of the B and C synchronization sequences in the synchronization data block; performing sliding calculation on the read partial baseband signal data by using a sequence which is generated by the optical transceiver and has the length of a B or C synchronization sequence in the synchronization data block and is the same as a binary sequence used when the optical transceiver generates the synchronization data block; and the demodulated baseband signal data corresponding to the maximum value in the sliding calculation result is the time synchronization position.

In the above scheme, the received signal processing module is specifically configured to perform frequency offset estimation on a baseband signal after time synchronization; and eliminating the carrier frequency deviation according to the result of the frequency deviation estimation, and performing channel estimation on the baseband signal after the carrier frequency deviation is eliminated.

In the foregoing solution, the received signal processing module is specifically configured to generate a UW sequence with a length of M according to a manner that an optical transmitter generates the UW sequence, and perform correlation calculation using the generated UW sequence and a baseband signal from which a carrier frequency offset is removed to obtain a channel estimation result.

The SC-FDE-based signal processing method, the device and the system have the following advantages and characteristics: the UW sequence generated by the optical transmitter uses a binary sequence, and the binary sequence is simpler than a CAZAC sequence, so that the optical transmitter does not need to use a high-end and complex DAC (digital-to-analog converter), thereby simplifying the hardware equipment of the optical transmitter and reducing the cost of the optical transmitter;

in addition, the invention uses the self-generated synchronous data block to perform sliding calculation on the received super frame in the optical receiver to perform time synchronization, and because only one synchronous data block is in one super frame, the method is more accurate than the prior method for performing synchronization according to two identical UW sequences of each data frame; the problem that related peaks are not sharp enough in Schmidl synchronous calculation can be avoided by using sliding calculation, and the sliding calculation is more accurate than the Schmidl synchronous calculation;

the optical receiver of the invention uses the correlation calculation to obtain the channel estimation value, and the correlation calculation can be compared with the maximum likelihood estimation method used in the existing method, and the correlation calculation does not need inverse matrix operation, so the invention has the advantages of small operation amount and less occupied resources.

Drawings

FIG. 1 is a diagram illustrating a data frame structure in the prior art;

FIG. 2 is a schematic diagram of a signal processing flow of an optical transceiver in the SC-FDE-based signal processing method according to the present invention;

FIG. 3 is a block diagram of a synchronous data block generated in the optical transmitter according to the present invention;

fig. 4 is a schematic diagram of a super frame structure in the optical transmitter of the present invention;

FIG. 5 is a schematic diagram of a signal processing flow of an optical receiver in the SC-FDE-based signal processing method according to the present invention;

FIG. 6 is a schematic diagram of the SC-FDE-based signal processing system according to the present invention.

Detailed Description

The basic idea of the invention is: the optical transmitter generates a UW sequence and a synchronous data block, the UW sequence is used for forming a data frame, the synchronous data block and the data frame are used for forming a super frame, and the super frame is used as a baseband signal to be sent to the optical receiver; after receiving the baseband signal, the optical receiver performs sliding calculation on the received super frame by using the synchronous data block to perform time synchronization, and performs correlation calculation by using the UW sequence to obtain a channel estimation value.

The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.

The signal processing flow of the optical transmitter in the SC-FDE-based signal processing method of the present invention is shown in fig. 2, and includes the following steps:

step 101: the optical transmitter generates a UW sequence and a synchronization Data block, and uses the UW sequence and Data to be transmitted to form a Data frame, and uses a synchronization Data block and a plurality of Data frames to form a super frame.

Here, the generating UW sequence is: the UW sequence is composed using binary sequences, which can be selected according to the following conditions:

u(n)∈{+1，-1}，n＝0，1，...，M-1；

u (n) the length of the sequence is a multiple of 4;

the M/2-1 and M-1 in u (n) are set to-1;

the first and second halves of the sequence are in complementary relationship: u (n) ═ u (n + M/2), n ═ 0., M/2-2.

The binary sequence is an existing sequence in the prior art and is not described herein; the way of selecting the binary sequence according to the above conditions is the prior art, and is not described herein;

the synchronous data block is: the method consists of A, B, C segments of synchronization sequences, as shown in fig. 3, the length of the segment A is L bits, and the length of the segment B and the segment C are both N bits; wherein, the L bits of data of the a sync sequence are a binary sequence s' (N) (N ═ N/2-L.., N/2-1); the B and C synchronization sequences are sync (n), sync (n) ═ s' (n) x (n); wherein x (N) is a binary sequence with length N, and the conditions for selecting the binary sequence of x (N) are the same as the conditions for generating the UW sequence:

n is the length of x (N), k is 0, 1.

x(n)∈{+1，-1}，n＝0，1，...，N-1；

x (n) the length of the sequence is a multiple of 4;

the N/2-1 and the N-1 in x (N) are set to-1;

the first and second halves of the sequence are in complementary relationship: x (N) — x (N + N/2), N ═ 0.

The s' (n) may be according to conditions

And (6) selecting.

The constituent data frames are: respectively adding two same UWs with the length of M at the front end and the rear end of the Data to form a Data frame; the constituent super frames are: the sync block is added before the Data frames as shown in fig. 4, wherein the super frame includes one sync block and a plurality of Data frames, each Data frame including two UWs and one piece of Data. Wherein the number of the subframes is determined according to the number of the subframes contained in the super frame specified in the prior art.

In addition, since the optical transmitter in the prior art generates two baseband signals with different polarization states, while the operation of step 101 is performed, a UW sequence and a synchronous Data block with another polarization state are generated in the same way, a Data frame is composed of the UW sequence with the polarization state and Data to be transmitted, and a super frame is composed of one synchronous Data block and a plurality of Data frames;

wherein the UW sequence of the other polarization state may be d cyclic shifts of one of the two polarization states; the synchronization data block of the other polarization state is identical to one of the two polarization states.

Step 102: the optical transmitter modulates the baseband signal composed of the super frames into a modulation signal and transmits the modulation signal to the optical receiver.

Here, the modulation is the prior art, the specific modulation process is not described herein, and a Mach-Zehnder (Mach-Zehnder) modulator may be used to modulate the baseband signal.

The signal processing flow of the optical receiver in the SC-FDE-based signal processing method of the present invention is shown in fig. 5, and includes the following steps:

step 201: after receiving the modulated signal from the optical transmitter, the optical receiver demodulates the modulated signal to obtain a baseband signal.

Here, the demodulation is the prior art, and the specific demodulation process is not described herein;

the demodulation resulting baseband signal can be expressed as:

wherein, r (n) represents the baseband signal obtained by the demodulation of the optical receiver; r is₁(n) and r₂(n) baseband signals of two polarization states obtained by demodulation of the optical receiver are respectively represented; Δ ω is the carrier frequency deviation, T_sSampling a time interval frequency for an Analog-to-Digital converter (ADC); w (n) is white Gaussian noise; h (k) is an impulse response function expression, which is the prior art and is not described herein; s₁(n) and s₂And (n) respectively representing the baseband signals of the two polarization states generated by the optical transmitter.

Step 202: and the optical receiver performs sliding calculation on the demodulated baseband signal to perform time synchronization.

Here, the performing time synchronization on the sliding calculation of the received superframe includes: the optical receiver starts to read data with the length larger than 2N from any bit data in the demodulated baseband signals of the two polarization states as synchronous calculation signals; utilizing self-generated x (N) with length of N to make sliding calculation for the above-mentioned read synchronous calculation signal; the demodulated baseband signal data corresponding to the maximum value in the sliding calculation result is the time synchronization position;

the time synchronization position is the frame header position of the demodulated baseband signal, namely the frame header of the baseband signal can be found by determining the time synchronization position;

the maximum of the results of the slip calculation is: if the maximum value is not obtained after the calculation of the baseband signal with the length being greater than 2N read this time, reading the baseband signal with the length being greater than 2N again from the baseband signal read this time until the maximum value in the result of the sliding calculation is obtained; the maximum value may be determined according to whether the result of the sliding calculation is greater than a preset threshold value, for example, the threshold value may be preset to be 0.9;

n represents the length of the B or C synchronization sequence in the synchronization data block; x (N) is a binary sequence used when the optical transceiver generates the synchronous data block, the sequence is generated in the optical receiver by using the same method of the optical transceiver, the length of the sequence is the same as that of the optical transceiver, and the sequence is N;

the slip calculation may comprise the following calculation steps:

M (m) = \frac{| P_{1} (m) |}{R_{1} (m)} + \frac{| P_{2} (m) |}{R_{2} (m)};

the position of the time synchronization is m (m), and the position of the data m with the maximum value can be expressed as:

\hat{d} = \arg \max_{m} (M (m)) .

step 203: and the optical receiver carries out frequency deviation estimation on the synchronized baseband signals, eliminates the frequency deviation according to the frequency deviation estimation result and obtains the baseband signals with the frequency deviation eliminated.

Here, the frequency offset estimation may be: performing correlation calculation on data with the length of more than 2N read from the frame header position of the synchronized baseband signal by using x (N) with the length of N generated in the step 202, and substituting different frequencies for calculation to obtain a frequency offset value corresponding to the maximum value in the result, namely the finally obtained frequency offset estimation value;

wherein the correlation calculation may use the formula:

the frequency offset value corresponding to the maximum value may be represented as:

the elimination of the frequency offset according to the frequency offset estimation result is the prior art, and may include: and performing frequency adjustment on the received synchronized baseband signal by using the calculated frequency deviation estimation value to obtain a frequency-adjusted baseband signal.

Further, if the user needs more accurate frequency offset estimation, the user may perform a second frequency offset estimation on the baseband signal after the frequency offset is eliminated once, and then eliminate the frequency offset according to the frequency offset estimation result to obtain the baseband signal after the frequency offset is eliminated.

Wherein the second frequency offset estimation uses the formula:

different frequencies are brought in for calculation, and then the maximum value in the obtained result is utilized by a formulaAnd calculating a second frequency deviation estimated value.

Step 204: the optical receiver performs channel estimation on the baseband signal from which the frequency offset is removed.

Here, the baseband signal from which the carrier frequency offset is removed may be expressed as:

the performing channel estimation comprises: the optical receiver generates a UW sequence with the length of M according to the mode that the optical receiver generates the UW sequence, and performs correlation calculation by using the UW sequence generated by the optical receiver and the baseband signal with the carrier frequency deviation eliminated to obtain a channel estimation result;

wherein the correlation calculation may use the following formula:

wherein u (k) is a UW sequence generated by the optical receiver and has a length M;

if the cyclic shift d of the UW sequence on one polarization state relative to the UW sequence on the other polarization state satisfies L ≦ d < M/2- (L-1):

<math> <mrow> <munderover> <mi>Σ</mi> <mrow> <mi>k</mi> <mo>=</mo> <mn>0</mn> </mrow> <mrow> <mi>M</mi> <mo>-</mo> <mn>1</mn> </mrow> </munderover> <msub> <mi>u</mi> <mn>1</mn> </msub> <mrow> <mo>(</mo> <mi>n</mi> <mo>+</mo> <mi>k</mi> <mo>-</mo> <mi>l</mi> <mo>)</mo> </mrow> <msubsup> <mi>u</mi> <mn>1</mn> <mo>*</mo> </msubsup> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> <mo>=</mo> <mn>0</mn> <mo>,</mo> <mi>n</mi> <mo>&NotEqual;</mo> <mi>l</mi> <mo>,</mo> <mi>n</mi> <mo>,</mo> <mi>l</mi> <mo>=</mo> <mn>0,1</mn> <mo>,</mo> <mo>.</mo> <mo>.</mo> <mo>.</mo> <mo>,</mo> <mi>L</mi> <mo>-</mo> <mn>1</mn> <mo>,</mo> </mrow> </math>

<math> <mrow> <munderover> <mi>Σ</mi> <mrow> <mi>k</mi> <mo>=</mo> <mn>0</mn> </mrow> <mrow> <mi>M</mi> <mo>-</mo> <mn>1</mn> </mrow> </munderover> <msub> <mi>u</mi> <mn>2</mn> </msub> <mrow> <mo>(</mo> <mi>n</mi> <mo>+</mo> <mi>k</mi> <mo>-</mo> <mi>l</mi> <mo>)</mo> </mrow> <msubsup> <mi>u</mi> <mn>2</mn> <mo>*</mo> </msubsup> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> <mo>=</mo> <mn>0</mn> <mo>,</mo> <mi>n</mi> <mo>&NotEqual;</mo> <mi>l</mi> <mo>,</mo> <mi>n</mi> <mo>,</mo> <mi>l</mi> <mo>=</mo> <mn>0</mn> <mo>,</mo> <mo>.</mo> <mo>.</mo> <mo>.</mo> <mo>,</mo> <mi>L</mi> <mo>-</mo> <mn>1</mn> <mo>.</mo> </mrow> </math>

is provided with h₁＝[h₁₁(0)，...，h₁₁(L-1)，h₁₂(0)，...，h₁₂(L-1)]^T，

h₂＝[h₂₁(0)，...，h₂₁(L-1)，h₂₂(0)，...，h₂₂(L-1)]^T，

The following can be obtained:

h_{1} = \frac{1}{M} (y_{1} - w_{1}),

h_{2} = \frac{1}{M} (y_{2} - w_{2});

wherein h is₁、h₂Channel impulse response function, y, representing two polarization states₁、y₂The result of the correlation calculation of the baseband signal representing the two polarization states with the UW sequence, w₁、w₂Representing noise in both polarization states;

when in the above formula w₁、w₂Zero, the resulting h₁、h₂The channel estimates for the two polarization states can be expressed as:

{\hat{h}}_{1} = \frac{1}{M} y_{1},

{\hat{h}}_{2} = \frac{1}{M} y_{2} .

as shown in fig. 6, the present invention provides an SC-FDE-based signal processing system, which includes: an optical transmitter 21 and an optical receiver 22; wherein,

an optical transmitter 21 for generating a UW sequence and a synchronous data block, forming a data frame by the UW sequence, forming a super frame by the synchronous data block and the data frame, and transmitting the super frame to the optical receiver 22 as a baseband signal;

and the optical receiver 22 is configured to perform time synchronization on the received super frame by performing sliding calculation on the received super frame by using the synchronization data block after receiving the baseband signal sent by the optical transmitter 21, and then perform channel estimation by using the UW sequence.

The optical transmitter 21 is specifically configured to use a binary sequence to form a UW sequence, and the binary sequence may be selected according to the following conditions:

u(n)∈{+1，-1}，n＝0，1，...，M-1；

The length of the u (n) sequence is a multiple of 4;

the M/2-1 and M-1 in u (n) are set to-1;

The optical transmitter 21 is specifically configured to generate a binary sequence s' (N) with a length of L symbols as an a synchronization sequence when generating a synchronization data block, and generate a binary sequence sync (N) with a length of N as a B and C synchronization sequences;

where, sync (N) ═ s' (N) x (N), and x (N) is a binary sequence having a length of N, and the conditions for selecting the binary sequence of x (N) are the same as those for generating the UW sequence:

n is the length of x (N), k is 0, 1.

x(n)∈{+1，-1}，n＝0，1，...，N-1；

x (n) the length of the sequence is a multiple of 4;

the N/2-1 and the N-1 in x (N) are set to-1;

the first and second halves of the sequence are in complementary relationship: x (N) -x (N + N/2), N-0, N/2-2;

s' (n) may be dependent on conditions

And (6) selecting.

The optical transmitter 21 is specifically configured to add two UWs with the same length M to the front and back ends of the Data, respectively, to form a Data frame; the synchronous data block is added before a plurality of data frames to form a super frame.

The optical transmitter 21 is specifically configured to generate two baseband signals with different polarization states according to the prior art, so that while generating a super frame, a UW sequence and a synchronization Data block with another polarization state are generated in the same manner, the UW sequence and Data to be transmitted form a Data frame, and the synchronization Data block and a plurality of Data frames form the super frame; wherein the further sequence of polarization states UW may be d cyclic shifts of the UW sequence of the other of the two polarization states; the synchronization data block of the other polarization state is identical to one of the two polarization states.

The optical transmitter 21 is further configured to use the super frame as a baseband signal, modulate the baseband signal, and transmit the modulated baseband signal to the optical receiver 22; correspondingly, the optical receiver 22 is further configured to receive the modulated signal sent by the optical transmitter 21, and demodulate the modulated signal to obtain a baseband signal.

The optical receiver 22 is specifically configured to read data with a length greater than 2N from any one bit of data in the demodulated baseband signals in the two polarization states as a synchronous calculation signal; utilizing self-generated x (N) with length of N to make sliding calculation for the above-mentioned read synchronous calculation signal; the demodulated baseband signal data corresponding to the maximum value in the sliding calculation result is the time synchronization position;

wherein N represents the length of the B or C synchronization sequence in the synchronization data block; x (N) is a binary sequence used by optical transceiver 21 to generate the sync block, which is generated by optical receiver 22 using the same method as optical transceiver 21, and has the same length as optical transceiver 21, N;

the slip calculation may comprise the following calculation steps:

M (m) = \frac{| P_{1} (m) |}{R_{1} (m)} + \frac{| P_{2} (m) |}{R_{2} (m)};

\hat{d} = \arg \max_{m} (M (m)) .

the optical receiver 22 is further configured to perform frequency deviation estimation on the synchronized baseband signal, and eliminate the frequency deviation according to a frequency deviation estimation result to obtain a baseband signal with the frequency deviation eliminated.

The optical receiver 22 is specifically configured to, when performing frequency offset estimation, perform correlation calculation on data with a length greater than 2N read from a frame header position of a synchronized baseband signal by using x (N) with a length of N generated by the optical receiver, and bring the data into different frequencies to perform calculation, where a frequency offset value corresponding to a maximum value in an obtained result is a finally obtained frequency offset estimation value;

wherein the correlation calculation may use the formula:

the frequency offset value corresponding to the maximum value may be represented as: the frequency offset value is indicated.

Further, if the user needs more accurate frequency deviation estimation, the second frequency deviation estimation is performed on the baseband signal subjected to the first frequency deviation elimination, and then the frequency deviation is eliminated according to the frequency deviation estimation result, so that the baseband signal subjected to the frequency deviation elimination is obtained.

Wherein the second frequency offset estimation uses the formula:

The optical receiver 22 is specifically configured to perform channel estimation on the baseband signal without the carrier frequency offset;

the baseband signal after carrier frequency offset cancellation can be represented as:

the optical receiver 22 is specifically configured to generate a UW sequence with a length of M in a manner that the optical transmitter 21 generates the UW sequence, and perform correlation calculation using the UW sequence generated by the optical receiver and the baseband signal from which the carrier frequency offset is removed to obtain a channel estimation result;

wherein the correlation calculation may use the following formula:

where u (k) is a UW sequence generated by the optical receiver 22, and has a length M;

<math> <mrow> <munderover> <mi>Σ</mi> <mrow> <mi>k</mi> <mo>=</mo> <mn>0</mn> </mrow> <mrow> <mi>M</mi> <mo>-</mo> <mn>1</mn> </mrow> </munderover> <msub> <mi>u</mi> <mn>2</mn> </msub> <mrow> <mo>(</mo> <mi>n</mi> <mo>+</mo> <mi>k</mi> <mo>-</mo> <mi>l</mi> <mo>)</mo> </mrow> <msubsup> <mi>u</mi> <mn>2</mn> <mo>*</mo> </msubsup> <mrow> <mo>(</mo> <mi>k</mi> <mo>)</mo> </mrow> <mo>=</mo> <mn>0</mn> <mo>,</mo> <mi>n</mi> <mo>&NotEqual;</mo> <mi>l</mi> <mo>,</mo> <mi>n</mi> <mo>,</mo> <mi>l</mi> <mo>=</mo> <mn>0</mn> <mo>,</mo> <mo>.</mo> <mo>.</mo> <mo>.</mo> <mo>,</mo> <mi>L</mi> <mo>-</mo> <mn>1</mn> </mrow> </math>

h₂＝[h₂₁(0)，...，h₂₁(L-1)，h₂₂(0)，...，h₂₂(L-1)]^T，

Wherein h is₁、h₂Channel impulse response function, y, representing two polarization states₁、y₂The result of the correlation calculation of the baseband signal representing the two polarization states with the UW sequence, w₁、w₂Representing noise in both polarization states; when in the above formula w₁、w₂Zero, the resulting h₁、h₂The channel estimates for the two polarization states can be expressed as:

h_{1} = \frac{1}{M} (y_{1} - w_{1}),

h_{2} = \frac{1}{M} (y_{2} - w_{2})

the channel estimates for each of the two polarization states are:

the optical transmitter 21 includes: a transmission signal processing module 211 and an optical modulation module 212; wherein,

a transmission signal processing module 211, configured to generate a UW sequence and a synchronous data block, form a data frame with the UW sequence, form a super frame with the synchronous data block and the data frame, and send the super frame to the optical modulation module 212;

the optical modulation module 212 is configured to receive the superframe sent from the sending signal processing module 211 as a baseband signal, modulate the baseband signal, and send the modulated baseband signal to the optical receiver 22.

The sending signal processing module 211 is specifically configured to use a binary sequence to form a UW sequence, and the binary sequence may be selected according to the following conditions:

u(n)∈{+1，-1}，n＝0，1，...，M-1；

The length of the u (n) sequence is a multiple of 4;

the M/2-1 and M-1 in u (n) are set to-1;

The sending signal processing module 211 is specifically configured to generate L symbol-long binary sequences s' (N) as an a synchronization sequence when generating a synchronization data block, and generate N-long binary sequences sync (N) as B and C synchronization sequences;

n is the length of x (N), k is 0, 1.

x(n)∈{+1，-1}，n＝0，1，...，N-1；

x (n) the length of the sequence is a multiple of 4;

the N/2-1 and the N-1 in x (N) are set to-1;

s' (n) may be dependent on conditions

And (6) selecting.

The sending signal processing module 211 is specifically configured to add two UWs with the same length M to the front and back ends of the Data, respectively, to form a Data frame; the synchronous data block is added before a plurality of data frames to form a super frame.

The transmission signal processing module 211 is specifically configured to generate two baseband signals with different polarization states according to the prior art, so that while generating a superframe, a UW sequence and a synchronization Data block with another polarization state are generated in the same manner, the UW sequence and Data to be transmitted form a Data frame, and the synchronization Data block and a plurality of Data frames form the superframe; wherein the further sequence of polarization states UW may be d cyclic shifts of the UW sequence of the other of the two polarization states.

The optical receiver 22 includes: a received signal processing module 221 and a light demodulation module 222; wherein,

an optical demodulation module 222, configured to receive the modulated signal sent by the optical transmitter 21, demodulate the modulated signal to obtain a baseband signal, and send the demodulated baseband signal to the received signal processing module 221;

the received signal processing module 221 is configured to perform time synchronization on the received super frame by using a sliding calculation performed by the synchronization data block after receiving the baseband signal sent by the optical demodulation module 222, and then perform channel estimation by using the UW sequence.

The received signal processing module 221 is specifically configured to read data with a length greater than 2N from any one bit of data in the demodulated baseband signals in the two polarization states as a synchronous calculation signal; utilizing self-generated x (N) with length of N to make sliding calculation for the above-mentioned read synchronous calculation signal; the demodulated baseband signal data corresponding to the maximum value in the sliding calculation result is the time synchronization position;

wherein N represents the length of the B or C synchronization sequence in the synchronization data block; x (N) is a binary sequence used by optical transceiver 21 to generate the sync block, which is generated by optical receiver 22 using the same method as optical transceiver 21, and is N as long as optical transceiver 21.

The received signal processing module 221 is further configured to perform frequency deviation estimation on the synchronized baseband signal, eliminate the frequency deviation according to the frequency deviation estimation result, and obtain the baseband signal with the frequency deviation eliminated.

The received signal processing module 221 is specifically configured to, when performing frequency offset estimation, perform correlation calculation by using data with a length greater than 2N, which is generated by itself and has a length of x (N) of N, read from a frame header position of a synchronized baseband signal, and bring the data into different frequencies to perform calculation, where a frequency offset position corresponding to a maximum value in an obtained result is a finally obtained frequency offset estimation value;

further, if a user needs more accurate frequency deviation estimation, the user may set to perform a second frequency deviation estimation on the baseband signal subjected to the first frequency deviation elimination, and then eliminate the frequency deviation according to a frequency deviation estimation result to obtain a baseband signal subjected to the frequency deviation elimination;

wherein the second frequency offset estimation uses the formula:

The received signal processing module 221 is specifically configured to perform channel estimation on the baseband signal after the carrier frequency offset is removed according to the result of the frequency offset estimation.

The received signal processing module 221 is specifically configured to generate a UW sequence with a length of M in a manner that the optical transmitter 21 generates the UW sequence, and perform correlation calculation using the generated UW sequence and the baseband signal without the carrier frequency offset to obtain a channel estimation result.

The above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention.

Claims

1. A signal processing method based on single carrier frequency domain equalization SC-FDE is characterized by comprising the following steps:

the optical transmitter generates a unique word UW sequence and a synchronous data block, two identical UW sequences are respectively added at the front end and the rear end of data to form a data frame, the synchronous data block is added in front of a plurality of data frames to form a super frame, and the super frame is used as a baseband signal to be sent to the optical receiver; the synchronous data block is: the method comprises A, B, C three sections of synchronization sequences, wherein the A section of synchronization sequence is L bits long, and the B and C synchronization sequences are both N bits long; wherein, the L bit data of the a synchronization sequence is a binary sequence s' (N) (N is N/2-L, …, N/2-1); the B and C sync sequences are sync (N), sync (N) s' (N) x (N), and x (N) is a binary sequence of length N, and the conditions for selecting x (N) binary sequences are the same as those for selecting binary sequences when generating UW sequences.

2. The method of claim 1, wherein generating the UW sequence comprises: the UW sequence was composed using binary sequences selected according to the following conditions:

u(n)∈{+1,-1}，n＝0,1,...,M-1；

The length of the u (n) sequence is a multiple of 4;

the M/2-1 and M-1 in u (n) are set to-1;

u(n)＝-u(n+M/2),n＝0,...,M/2-2。

3. the method of claim 1, wherein s' (n) is determined according to conditions

And (6) selecting.

4. The method of claim 1, wherein after transmitting the superframe as a baseband signal to an optical receiver, the method further comprises: after receiving the baseband signal from the optical transmitter, the optical receiver performs sliding calculation on the received super frame by using the synchronous data block to perform time synchronization, and performs correlation calculation by using the UW sequence to obtain a channel estimation value.

5. The method of claim 4, wherein time synchronizing the received superframe with the synchronization data block by sliding computation comprises:

6. The method of claim 4, wherein before the obtaining the channel estimation value by using the UW sequence for the correlation calculation, the method further comprises: the optical receiver carries out frequency deviation estimation on the baseband signals after time synchronization; and eliminating the carrier frequency deviation according to the result of the frequency deviation estimation, and performing channel estimation on the baseband signal after the carrier frequency deviation is eliminated.

7. The method of claim 6, wherein the performing channel estimation on the baseband signal after removing the carrier frequency offset comprises: the optical receiver generates a UW sequence with the length of M according to the mode that the optical receiver generates the UW sequence, and performs correlation calculation by using the UW sequence generated by the optical receiver and the baseband signal with the carrier frequency deviation eliminated, so as to obtain a channel estimation result.

8. A method for SC-FDE-based signal processing, the method comprising:

after receiving a baseband signal sent by the optical transmitter, the optical receiver performs sliding calculation on the received super frame by using a synchronous data block to perform time synchronization, and performs correlation calculation by using a UW sequence to obtain a channel estimation value; the baseband signal is a super frame formed by adding a synchronous data block before a plurality of data frames formed by respectively adding two identical UW sequences at the front end and the rear end of data; the synchronous data block is: the method comprises A, B, C three sections of synchronization sequences, wherein the A section of synchronization sequence is L bits long, and the B and C synchronization sequences are both N bits long; wherein, the L bit data of the a synchronization sequence is a binary sequence s' (N) (N is N/2-L, …, N/2-1); the B and C sync sequences are sync (N), sync (N) s' (N) x (N), and x (N) is a binary sequence of length N, and the conditions for selecting x (N) binary sequences are the same as those for selecting binary sequences when generating UW sequences.

9. The method of claim 8, wherein before the optical receiver receives the baseband signal from the optical transmitter, the method further comprises: the optical transmitter generates UW sequences and synchronization data blocks, and the UW sequences are used to compose the data frames.

10. The method of claim 9, wherein generating the UW sequence comprises: the UW sequence was composed using binary sequences selected according to the following conditions:

u(n)∈{+1,-1}，n＝0,1,...,M-1；

The length of the u (n) sequence is a multiple of 4;

the M/2-1 and M-1 in u (n) are set to-1;

u(n)＝-u(n+M/2),n＝0,...,M/2-2。

11. the method of claim 9, wherein s' (n) is determined according to a condition

And (6) selecting.

12. The method of claim 8, wherein time synchronizing the received superframe with a sliding calculation using a synchronization data block comprises:

13. The method of claim 8, wherein before the obtaining the channel estimation value by using the UW sequence for the correlation calculation, the method further comprises: the optical receiver carries out frequency deviation estimation on the baseband signals after time synchronization; and eliminating the carrier frequency deviation according to the result of the frequency deviation estimation, and performing channel estimation on the baseband signal after the carrier frequency deviation is eliminated.

14. The method of claim 13, wherein performing channel estimation on the baseband signal after removing the carrier frequency offset comprises: the optical receiver generates a UW sequence with the length of M according to the mode that the optical receiver generates the UW sequence, and performs correlation calculation by using the UW sequence generated by the optical receiver and the baseband signal with the carrier frequency deviation eliminated, so as to obtain a channel estimation result.

15. An SC-FDE based signal processing system, comprising: an optical transmitter and an optical receiver; wherein,

the optical transmitter is used for generating UW sequences and synchronous data blocks, adding the two same UW sequences to the front end and the rear end of data respectively to form a data frame, adding the synchronous data blocks to the front ends of a plurality of data frames to form a super frame, and sending the super frame to the optical receiver as a baseband signal;

the optical receiver is used for performing sliding calculation on the received super frame by using the synchronous data block to perform time synchronization after receiving a baseband signal sent by the optical transmitter, and then performing channel estimation by using the UW sequence; the synchronous data block is: the method comprises A, B, C three sections of synchronization sequences, wherein the A section of synchronization sequence is L bits long, and the B and C synchronization sequences are both N bits long; wherein, the L bit data of the a synchronization sequence is a binary sequence s' (N) (N is N/2-L, …, N/2-1); the B and C sync sequences are sync (N), sync (N) s' (N) x (N), and x (N) is a binary sequence of length N, and the conditions for selecting x (N) binary sequences are the same as those for selecting binary sequences when generating UW sequences.

16. An optical transmitter, comprising: the device comprises a sending signal processing module and an optical modulation module; wherein,

the transmission signal processing module is used for generating UW sequences and synchronous data blocks, adding the two same UW sequences to the front end and the rear end of data respectively to form data frames, adding the synchronous data blocks to the front ends of a plurality of data frames to form super frames, and transmitting the super frames to the light modulation module; the synchronous data block is: the method comprises A, B, C three sections of synchronization sequences, wherein the A section of synchronization sequence is L bits long, and the B and C synchronization sequences are both N bits long; wherein, the L bit data of the a synchronization sequence is a binary sequence s' (N) (N is N/2-L, …, N/2-1); the B and C synchronization sequences are sync (N), sync (N) s' (N) x (N), and x (N) is a binary sequence of length N, and the conditions for selecting x (N) binary sequences are the same as those for selecting binary sequences when generating UW sequences;

17. An optical transmitter in accordance with claim 16,

the transmitting signal processing module is specifically configured to use a binary sequence to form a UW sequence, and select the binary sequence according to the following conditions:

u(n)∈{+1,-1}，n＝0,1,...,M-1；

The length of the u (n) sequence is a multiple of 4;

the M/2-1 and M-1 in u (n) are set to-1;

u(n)＝-u(n+M/2),n＝0,...,M/2-2。

18. an optical transmitter in accordance with claim 16,

the s' (n) may be according to conditions

And (6) selecting.

19. An optical receiver, comprising: a received signal processing module and an optical demodulation module; wherein,

the received signal processing module is used for performing sliding calculation on the received super frame by using the synchronous data block to perform time synchronization after receiving the baseband signal sent by the optical demodulation module, and then performing channel estimation by using the UW sequence; the baseband signal is a super frame formed by adding a synchronous data block before a plurality of data frames formed by respectively adding two identical UW sequences at the front end and the rear end of data; the synchronous data block is: the method comprises A, B, C three sections of synchronization sequences, wherein the A section of synchronization sequence is L bits long, and the B and C synchronization sequences are both N bits long; wherein, the L bit data of the a synchronization sequence is a binary sequence s' (N) (N is N/2-L, …, N/2-1); the B and C sync sequences are sync (N), sync (N) s' (N) x (N), and x (N) is a binary sequence of length N, and the conditions for selecting x (N) binary sequences are the same as those for selecting binary sequences when generating UW sequences.

20. The optical receiver of claim 19,

the receiving signal processing module is specifically configured to read data in the baseband signals in the two polarization states, where the length of the data is greater than the sum of the lengths of the B and C synchronization sequences in the synchronization data block; performing sliding calculation on the read partial baseband signal data by using a sequence which is generated by the optical transceiver and has the length of a B or C synchronization sequence in the synchronization data block and is the same as a binary sequence used when the optical transceiver generates the synchronization data block; and the demodulated baseband signal data corresponding to the maximum value in the sliding calculation result is the time synchronization position.

21. The optical receiver of claim 20,

the received signal processing module is specifically configured to perform frequency deviation estimation on the baseband signal after time synchronization; and eliminating the carrier frequency deviation according to the result of the frequency deviation estimation, and performing channel estimation on the baseband signal after the carrier frequency deviation is eliminated.

22. The optical receiver of claim 21,

the receiving signal processing module is specifically configured to generate a UW sequence with a length of M in a manner of generating the UW sequence by an optical transmitter, and perform correlation calculation by using the generated UW sequence and a baseband signal from which a carrier frequency offset is removed to obtain a channel estimation result.